EEG Activation Procedures

This set covers vocabulary and key concepts regarding EEG activation procedures including hyperventilation, photic stimulation, and sleep deprivation based on neurophysiology lecture notes.

Activation Procedures

Any procedure designed to enhance or elicit normal or abnormal EEG activities, especially epileptiform abnormalities.

Hyperventilation

The oldest known EEG activating procedure involving deep breathing for at least three minutes (up to five for children) at a rate of $15-20$ breaths per minute.

Normal Response to Hyperventilation

Increase in posterior background rhythm amplitude and a build up of medium to high amplitude bisynchronous intermixed delta and theta frequency activity.

Hypoglycaemia (HV Effect)

A condition where Glucose $<80\,mg/dL$ may result in a dramatic or prolonged response to hyperventilation in adults.

TIRDA

Temporal Intermittent Rhythmic Delta Activity; the most common localized slowing provoked by hyperventilation, often suggesting underlying epileptogenic pathology.

Delayed Symmetrical or Lateralised Slowing

Slowing in the post hyperventilation period that could suggest vascular insufficiency or Moya Moya disease if occurring 5 minutes post HV.

Hyperventilation Contraindications

Conditions including acute stroke (CVA), recent intracranial haemorrhage (ICH), large vessel severe stenosis, documented Moya Moya disease, severe cardiac/pulmonary disease, sickle cell disease, uncontrolled hypertension, and pregnancy.

Photic Stimulation

Activation performed with a strobe light between $1$ and $30\,Hz$ situated no more than $30\,cm$ from the eyes for 10 seconds total.

Photic Driving Response

A normal rhythmic, occipital dominant waveform response that is time locked to flash frequency.

Photoepileptiform Response

A paroxysmal spike/polyspike and wave activity following flash stimulus, strongly associated with Generalised Epilepsy and usually occurring between $15$ and $25\,Hz$.

Sleep Deprivation

An activating procedure where the first epileptiform discharge usually occurs in the first $15-30$ minutes of sleep (stages 1-3).

Juvenile Myoclonic Epilepsy (JME)

A generalised seizure disorder where photic stimulation is primarily activating.